The influence of protein oxidation on structure, pepsin diffusion, and in vitro gastric digestion of SPI emulsion

The stability behaviors of oxidized SPI emulsions under in vitro gastric conditions and the effects of pepsin diffusion on the proteolysis of emulsions were investigated using a static gastric model and the fluorescence recovery after photobleaching method. Results showed that protein oxidation increased the particle size of droplets and decreased the viscoelasticity of the interfacial layer. Compared to the control group (82.81 m2/s), the pepsin diffusivity decreased to 68.52 m2/s (7LA + LOX group) due to the space hindrance of oil droplets. After gastric digestion, protein hydrolysates were re-absorbed on the oil-water interface and formed a thick layer, thereby decreasing the size of oil droplets and reducing the contents of free amino acids in gastric digesta. The protein oxidation may affect the adsorption of interfacial proteins and alter the distribution of droplets, decreasing pepsin diffusion and ultimately impairing the emulsion gastric digestion. And this should be considered in the design of emulsion as the controllable delivery system.

Automated summary

The effects of oxidized SPI emulsions on in vitro gastric stability and pepsin diffusion were investigated. The results showed that protein oxidation increased droplet size and decreased interfacial viscoelasticity. Pepsin diffusivity decreased due to the hindrance of oil droplets. After gastric digestion, protein hydrolysates formed a thick layer on the oil-water interface, reducing droplet size and free amino acid content. Protein oxidation affects interfacial protein adsorption and droplet distribution, impairing emulsion gastric digestion, which should be considered in the design of controllable delivery systems.